Edwards Aquifer Lessons Highlighted in Federal Climate Report

A site in Shavano Park over the Edwards Aquifer Recharge Zone, where rainfall helps to restore the limestone aquifer.

Updated December 3, 2018

The latest federal climate report had some dire warnings for South Texas, using case studies of how extreme weather is threatening its coastal region, the Rio Grande, and the Edwards Aquifer.

The second volume of the Fourth National Climate Assessment has drawn attention across the U.S., despite its quiet release on Black Friday. It follows on the heels of a United Nations science report this year warning time is running out to avoid the most catastrophic effects of global warming.

The latest U.S. report, a more than 1,600-page assessment, is the product of 12 federal agencies and 350 scientists. Texas Tech University professor Katharine Hayhoe, one of its lead authors, called it the most comprehensive and up-to-date assessment on how climate change is affecting the U.S. and how the country is responding.

“Climate change isn’t a distant issue anymore,” Hayhoe said in a webinar hosted by Climate Matters, an independent organization of scientists and journalists. “It’s affecting every single one of us, in every part of the U.S., across almost every sector.”

Texas is ground zero for these effects. Since 1980, 105 weather and climate events in Texas have caused at least $1 billion in damage, more than in any other state, Hayhoe said, citing information from the National Oceanic and Atmospheric Organization.

“The release of the Fourth National Climate Assessment last week confirms the importance and urgency of action to both mitigate our local contributions to climate change and to adapt and prepare for not only future impacts, but those that we are experiencing now,” Doug Melnick, the City’s chief sustainability officer, said in an email.

Here are some of the key takeaways from the report for San Antonio:

Hurricanes

Hurricane Harvey, after making landfall in August 2017, was the second-most expensive storm in U.S. history, causing $125 billion in damage, according to NOAA estimates. It dropped more rain, mostly over the Houston area, than any other storm ever recorded in the continental U.S.

The report projects that climate change is increasing the intensity of tropical storms and causing them to store more water, leading to heavier rainfall. One study it cited “concluded that the heaviest rainfall amounts from intense storms, including hurricanes, have increased by [6 to 7 percent], on average, compared to what they would have been a century ago.”

However, climate change does not appear to be causing a greater number of storms.

Scott Ball / Rivard Report

Days after Hurricane Harvey made landfall, a fisherman takes large steps across wetlands outside of Port Aransas near a boat that washed ashore during the storm.

Even in the 2017 hurricane season, “the number of storms was within the range of observed historical variability and does not alter the conclusion that climate change is unlikely to increase the overall number of storms on average,” the report states.

The Edwards Aquifer

The report uses the San Antonio region’s most precious drinking water source as a case study for how growing populations and more intense droughts in a warming world will put more pressure on water resources.

The Edwards Aquifer is a vast but drought-sensitive water-bearing rock layer that stretches across much of the urban corridor of Central Texas. The region is among the fastest-growing in the country in terms of population.

Texas’ population is expected to grow by more than 70 percent between 2020 and 2070, the report states, with most of that population growth in cities. State demographers predict that San Antonio will gain an additional 1 million people by 2040.

“Over this same period, water availability in the U.S. Southwest is projected to decrease due to a shift to a more drought-prone climate state,” the report states. That could decrease the amount of rainfall that recharges the aquifer.

As a result of legal battles over the aquifer, the San Antonio Water System has over 20 years been diversifying its sources of water through new projects like brackish groundwater desalination and the Vista Ridge pipeline.

Even so, most of San Antonio’s water from roughly 2040 through 2070 will continue to come from the Edwards, even during extreme drought, according to SAWS’ 2017 water management plan.

The Rio Grande

The river that forms Texas’ boundary with Mexico is the most important water source for the cities and farmlands of South Texas on both sides of the border.

Fed by snowpack in Colorado and New Mexico, the river is at risk of drought in its mountainous headwaters and from increased evaporation from the series of downstream reservoirs, such as Lake Amistad, that store water for both the U.S. and Mexico, the report states.

“Changes in regional precipitation patterns, including observed increases in extreme rainfall events as part of a regional ‘dipole’ dry-wet-dry-again pattern, will affect both drought and flood occurrence and intensity along the Rio Grande channel,” it states.

Robert Rivard / Rivard Report

The confluence of the Lower Pecos River and Rio Grande in Seminole Canyon State Park north of the Texas-Mexico border.

On a more positive note, the report cites “a growing number of adaptation strategies” along the Rio Grande to better manage the diminishing river. One example is the dissemination of thorough seasonal climate outlooks for the river in both English and Spanish to get information out to people who depend on the river.

Local adaptation

The report is full of examples of responses happening at the state and local levels and among institutions like corporations and universities, in the absence of federal action on climate.

On the federal level, President Donald Trump has pursued an agenda of rolling back of environmental regulations on industry and agriculture. Speaking to reporterslast week, Trump dismissed the assessment, saying, “I don’t believe it.”

In San Antonio, the City, CPS Energy, Navigant Consulting, and the University of Texas at San Antonio are leading a communitywide planning effort to respond to the local causes and effects of global warming.

Planners have said that San Antonio might have to cut its current emissions rate in half by 2040 meet its share of the goals of the most recent international climate agreement.

“Through the … planning process, we have learned that climate change is a priority for our community regardless of sector or demographics, and we need to tackle this challenge head-on and in a unified and collaborative manner,” Melnick said. “I encourage all residents and stakeholders to have their voices heard in this important and timely process.”

Interestingly, South Texas is among the few regions of the U.S. where a majority of adults “believe that global warming is mostly caused by human activities,” according to results of a 2016 poll by the Yale Program on Climate Communication. Hayhoe discussed the results in the Climate Matters webinar.

“I actually wouldn’t agree with that statement either, but I don’t think my reason is the same as everybody else’s,” Hayhoe said.

Hayhoe said that no natural factors can explain the current warming trend and that the Earth’s temperatures should actually be going down, on average.

“So I would say that global warming is not being caused mostly by human activities. It’s being caused entirely by human activities,” Hayhoe said. “Because if it were not for our emissions of heat-trapping gases, we would be getting cooler by now, not warmer.”

7 Ice-ages with warming periods in between and guess what? We weren’t around for any of them.
The sensors used to be located in neutral areas but now they have been surrounded by heat islands. Our official reading is at the airport which is now surrounded by heat trapping asphalt and heat producing vehicles. This is common for many sensors.